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Ch. 8 - Techniques of Integration
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
All textbooksHass 15th EditionCh. 8 - Techniques of IntegrationProblem 8.8.88a
Chapter 8, Problem 8.8.88a

88. The region in Exercise 87 is revolved about the x-axis to generate a solid.
a. Find the volume of the solid.

Verified step by step guidance
1
Identify the region described in Exercise 87, including the functions and the interval over which the region is defined. This is essential because the volume depends on the shape of the region being revolved.
Set up the volume integral using the disk or washer method since the solid is generated by revolving the region about the x-axis. The general formula for the volume is \(V = \pi \int_a^b [R(x)]^2 \, dx\), where \(R(x)\) is the radius of the disk at position \(x\).
Determine the radius function \(R(x)\), which is the distance from the x-axis to the curve defining the boundary of the region. If there are two curves, use the difference of their squares to form the washer method: \(V = \pi \int_a^b \left([R_{outer}(x)]^2 - [R_{inner}(x)]^2\right) \, dx\).
Substitute the expressions for \(R(x)\) (or \(R_{outer}(x)\) and \(R_{inner}(x)\)) and the limits of integration \(a\) and \(b\) into the integral to form the definite integral representing the volume.
Evaluate the integral (or set it up for evaluation) to find the volume of the solid. This may involve integrating polynomial, trigonometric, or other functions depending on the original region.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Volume of Solids of Revolution

This concept involves finding the volume of a 3D solid formed by rotating a 2D region around an axis. The volume is typically calculated using integral methods such as the disk or washer method, which sum up infinitesimal cross-sectional areas along the axis of rotation.
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Finding Volume Using Disks

Disk and Washer Methods

The disk method calculates volume by integrating the area of circular cross-sections perpendicular to the axis of rotation. The washer method extends this by subtracting inner radii when the solid has a hollow part, useful when the region is bounded by two curves.
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Disk Method Using y-Axis

Setting up Definite Integrals

To find the volume, one must correctly set up the definite integral with proper limits and integrand representing the radius (or radii) of the cross-sections. This requires understanding the region's boundaries and expressing the radius as a function of the variable of integration.
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Definition of the Definite Integral
Related Practice
Textbook Question

Lifetime of a tire Assume the random variable L in Example 2f is normally distributed with mean μ = 22,000 miles and σ = 4,000 miles.

a. In a batch of 4000 tires, how many can be expected to last for at least 18,000 miles?

1
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Textbook Question

81. Find the values of p for which each integral converges.

a. ∫ from 1 to 2 of [dx / (x (ln x)^p)]

Textbook Question

Using different substitutions

Show that the integral

∫((x² - 1)(x + 1))^(-2/3) dx

can be evaluated with any of the following substitutions.

a. u = 1/(x + 1)

What is the value of the integral?

Textbook Question

Finding volume: Find the volume of the solid generated by revolving the region bounded by the x-axis and the curve y = x sin(x), 0 ≤ x ≤ π, about

a. The y-axis.

(See Exercise 57 for a graph.)

Textbook Question

Evaluate ∫ sec θ dθ by:

a. Multiplying by (sec θ + tan θ) / (sec θ + tan θ) and then using a u-substitution.

Textbook Question

Centroid:

Find the centroid of the region cut from the first quadrant by the curve

y = 1/√(x + 1) and the line x = 3.